By Karen Van Heukelem
In recent years, cities across the United States have found that restoring their old train stations is a great way to attract people and commerce to downtown districts that have seen better days. These revitalization projects have picked up the pace in cities from Washington, D.C., to Los Angeles, and they seem to work best when old, original functions are preserved and mixed in with the new.
That’s precisely the direction that redevelopment of Denver’s historic Union Station has taken: The classic, Beaux Arts-style building, which opened in 1914, lost almost all of the train traffic that had once kept it hopping. In fact, the once-bustling terminal’s activity had withered to a point where just one Amtrak train passed through each day.
The glorious old building has now been repurposed as a fine hotel, but at ground level the railyard space behind it still serves as a transit station. (Traditional trains roll through, but now it’s busy mainly with the city’s light-rail service.) On a level below the railyard is a new bus concourse with 22 loading bays.
This combined transportation hub, which opened in the summer of 2014, has brought new life and prosperity to an area that had long been in decline.
The redevelopment project began in 2002 with a $900 million budget and was later supplemented by a $300 million federal transit grant. We at Colorado Hardscapes (Denver) were brought in by the general contractor, Kiewit Corp. of Omaha, Neb., for our expertise with decorative concrete. Once we became involved, our role expanded to include construction of the magnificent waterfeature that now flanks the main entrance to the train station.
We joined the project team in 2008. Our initial participation had to do with completing the underground bus concourse, which runs perpendicular to the rail lines that occupy ground level on the site. This part of the project was right up our alley: We’ve long had a reputation for large-scale projects involving decorative concrete, and devising what was basically a huge, ornamented box behind the hotel plaza played right to our strengths.
About a dozen years previously, however, we’d added fountains and waterfeatures to our list of capabilities – and in this case it worked out very well for us when part of the plaza space was set aside for installation of the grand waterfeature that now graces the space: We were a known entity, and when the time came, Kiewit turned to us to get the job done.
Designed by Commercial Aquatic Engineering (CAE) of Eden Prairie, Minn., the waterfeature was intended to “activate” the plaza space along Wynkoop Street. One of the challenges we faced came with submerging the fountain works into the street-level plaza. It was clear early on that we would be working in a constricted space; what wasn’t clear was how the weather would challenge our ability to get everything exactly right with the fountain system – not an easy task under any circumstances, but even trickier through what proved to be a long, cold spring.
We tackled everything associated with the waterfeature, basically a dancing, interactive, dry-deck fountain, including the plumbing, electricity, concrete and more. It all took years to design and finally build. In fact, we started talking about it with Kiewit and the design team as early as September 2008, blue-skying ideas and beginning to think in terms of budget.
By 2011, we were finally awarded the contract for the bus concourse and began our work on site. Access was always tricky and standards were high, but the experience we had below ground gave us valuable insights into the way the project worked – and familiarity with the sorts of hoops we’d have to jump through to keep everything moving forward with the waterfeature.
|The excavation for the vault and the fountain deck took place in a constricted plaza space to one side of the station’s main entrance. Even at this early stage, it’s possible to get a sense of the sheer physical scale of the project – and of the need to get all of the piping’s slopes and elevations right.|
To take just one example, job-site safety was a huge issue for the entire project. This meant weekly and sometimes daily meetings with Kiewit and the rest of the project team to go along with extensive safety-related paperwork and documentation. There were also daily work-status meetings to cover each day’s goals – all in an effort to resolve scheduling, traffic and access issues before they could get in the way.
To meet the project’s need to comply with Disadvantaged Business Enterprise goals required by terms of the federal grant, we brought on a subcontractor to complete some of the underground concrete and earthwork and help the project hit the target for participation by these businesses. In addition, we had to make certain that all fountain-system components had been built and assembled in the United States.
Toward the end of our work on the bus box, Kiewit wrote a change order to Colorado Hardscapes’ contract, adding the waterfeature to our participation in the project.
It’s a stunning composition, beautiful in every possible way on the surface, but all of us know that most of what we did will never be seen by anyone, as it’s all encased in concrete and buried underground. This includes more than 3,700 linear feet of pipes of various diameters; 1,700 cubic yards of cementitious material we used to lock in the pipes at the right levels in the correct positions; a 12-foot-wide by 50-foot-long underground equipment and water-storage vault; and 92 individual sequencing nozzles with lights. It all took an extraordinary amount of time and care to get everything right.
|To ease the process of positioning and fixing the elevations of the nozzles, we poured a base slab in the fountain space. After carefully marking the best approximations we could of pipe and canister placements, we imbedded sections of threaded rod in the concrete to enable us to anchor the pipes and make all the fine adjustments we knew the system would require.|
Kiewit had prepared a computer model of the waterfeature covering all of the pipes and various external connections. This helped clarify what was involved early on and enabled us to resolve access and timing issues with other contractors working in areas around us before any conflicts could arise.
The area beneath the fountain was to be excavated to a depth of five to six feet, while the vault was to reach ten feet below grade. Access was tricky for the earthwork crews, as was removal of material. To the greatest extent possible, the excavated material was stored on site for future use, but much of it had to be moved to remote locations because there wasn’t enough available space in the work area. Again, this was where the regular meetings and a general insistence on open communication worked in everyone’s favor.
Much of our work on the waterfeature took place in the spring of 2014, which would seem workable to anyone unfamiliar with life in the Mile High City. Unfortunately, the sorts of temperature fluctuations we put up with through months of underground construction threw us some challenges. Much of it had to do with the fact that differences between day and night temperatures caused dramatic expansion and contraction of our pipes. At times, you could hear the bonging sounds they made; some mornings, it sounded like an orchestra warming up for a performance.
|To lock the pipes in place, we started by pumping in a four-foot layer of low-strength concrete to a level just short of the canisters. Once we surveyed all components for placements and elevations, we poured a final layer of high-strength concrete and made ready for the crew that was to come in and install the decking.|
We constantly made a point of draining the lines for fear of freezing on cold, snowy days. The design documents called for a tolerance of one-thirty-second of an inch for each of the nozzle canisters, so every expansion/contraction movement in the pipes required more fine-tuning and re-adjusting.
This was an ongoing problem that needed resolving; happily, our construction superintendent hit on part of the solution in the form of a concrete base slab. This gave us a stable platform and enabled us to secure the pipes and drains to maintain precise elevations. Once the slab was in place, we called in a survey crew to lay out the points and elevations for the canisters and drains. Next, we used threaded rod and adjusting screws to set the drains and canisters at the proper elevations and locations, then welded stabilizing cross-braces to the rods.
We brought the survey crew back multiple times as our work moved along, repeatedly checking every elevation and placement to make certain that neither Mother Nature nor our ongoing activity on site had pushed anything out of alignment.
PUSHING FOR PERFECTION
We implemented another wise idea on site, this one having to do with locking the canisters precisely where they needed to be. After a last session of surveying, testing, and adjusting both pipes and canisters, our crew carefully installed flow fill – a low-strength concrete – in gradual lifts around all of the pipes. This technique secured the pipes and canisters up to a level just below the bottoms of the canisters – about four feet of material in all.
What this all resulted in was a typical cross-section that included six inches of the concrete base platform; four feet of flow fill, six inches of waterproofed concrete to encase the nozzles; and a top level including mortar-set granite pavers (installed by another contractor). At every step, we tested and retested to plumbing to ensure that nothing we were doing had caused any leaks.
|The equipment vault (which also contains a large tank for water storage) includes two pumps, three sand filters and a ten-foot-long stainless steel manifold along with an ultraviolet sanitizing system and control panels. The layout is as precise and well-organized as we could make it – a kindness to the operators and clear testimony to the value and precision of the plans the project team generated.|
By the time we placed pipes in the plaza, we’d already done much of the work of preparing the adjacent equipment vault, which measured 12 feet wide, 50 feet long and nine feet tall. Water storage and some of the circulation plumbing took up a little under half of the vault’s length, while the rest was filled with mechanical control equipment (two pumps, three sand filters and a ten-foot-long stainless steel manifold) along with an ultraviolet sanitizing system and various control panels.
The pumps move water through the system at a rate of 1,400 gallons per minute. Up to 10,000 gallons of water is stored in the vault and moves through an elaborate filtration sequence before being returned to the nozzles, now safe for people who might come in contact with the water.
|It hasn’t taken long for Denver’s Union Station to reclaim its role as a major urban hub. By day, it’s a magnet for tourists and families who come to play in the water; by night the plaza is a bright visual core for an array of dining spots. And both day and night, the station is once again a busy transit hub serving traditional interstate train traffic as well as local light-rail and bus systems.|
Throughout the process, we at Colorado Hardscapes collaborated with the staff at Hargreaves Associates, who acted as the project’s landscape architects, and with Commercial Aquatic Engineering, a waterfeature design/programming firm, to ensure that the feature they’d designed for Kiewit would run as intended. At several key points along the way, CAE inspected the site and validated our work. As we were wrapping up our tasks on the plaza, they came in to direct the start-up and programming.
In the time since the waterfeature was commissioned in July 2014, it’s become habitual for pedestrians in the area to pass by the old train station, which is now an urban hub all over again. On warm days, children and adults alike play in the splashing water, dine on new restaurant patios and gather to meet friends and colleagues.
We at Colorado Hardscapes are proud of the role we played in all of this, celebrating our city’s history and breathing new life into a long-neglected area that will thrive for decades to come.